CN108369842B

CN108369842B - Superconducting wire

Info

Publication number: CN108369842B
Application number: CN201580084489.8A
Authority: CN
Inventors: 山口高史; 永石龙起; 小西昌也; 山名健司; 本井见二
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2015-11-11
Filing date: 2015-11-11
Publication date: 2020-01-21
Anticipated expiration: 2035-11-11
Also published as: JPWO2017081762A1; KR102315482B1; US11665982B2; CN108369842A; WO2017081762A1; JP6465217B2; DE112015007114T5; US20180337323A1; KR20180080234A

Abstract

A superconducting wire (10) comprises a substrate (1) and a layer of superconducting material (5). The substrate (1) comprises a first main surface (1a) and a second main surface (1b) opposite to the first main surface (1 a). The layer of superconducting material (5) is arranged on the first main surface (1 a). The superconducting material layer (5) is provided so as to cover a side surface of the substrate (1) and at least a part of the second main surface (1b) in a width direction of the substrate (1) along at least a part of the superconducting wire (10) in a direction in which the superconducting wire (10) extends. The thickness of the superconducting material layer (5) on the first main surface (1a) varies in the width direction. The maximum thickness of the layer of superconducting material (5) on the second main surface (1b) is smaller than the maximum thickness of the layer of superconducting material (5) on the first main surface (1 a).

Description

Superconducting wire

Technical Field

The present invention relates to a superconducting wire, and more particularly, to a superconducting wire in which a superconducting material layer is formed on a substrate.

Background

In recent years, superconducting wires in which a superconducting material layer is formed on a metal substrate are being developed. In particular, oxide superconducting wires are attracting attention. The oxide superconducting wire includes a superconducting material layer made of an oxide superconductor, which is a high-temperature superconductor having a transition temperature equal to or higher than a temperature of liquid nitrogen.

Such an oxide superconducting wire is generally manufactured by forming an intermediate layer on an orientation-aligned metal substrate, forming an oxide superconducting material layer on the intermediate layer, and further forming a stabilization layer of silver (Ag) or copper (Cu) (refer to, for example, japanese patent laid-open No. 2013-12406 (PTD 1)).

Reference list

Patent document

PTD 1: japanese patent laid-open No. 2013-12406

Disclosure of Invention

Technical problem to be solved by the invention

The superconducting wire configured in the above-described manner has a multilayer structure in which a ceramic layer composed of an intermediate layer and a superconducting material layer is formed on a metal substrate. When such a superconducting wire is cooled to its critical temperature, the difference in thermal expansion coefficient between the metal substrate and the ceramic layer causes stress to be applied from the metal substrate to the ceramic layer in the multilayer structure. However, the ceramic layer cannot generate stress. Therefore, the bonding strength at the interface between the metal substrate and the ceramic layer is reduced, resulting in a problem that local peeling occurs at the edge of the ceramic layer. This easily causes breakage, deformation, and the like in a part of the superconducting material layer, thereby causing deterioration of superconducting characteristics.

An object of the present invention is to provide a superconducting wire having stable superconducting characteristics by suppressing local peeling of a superconducting material layer.

Solution to the problem

A superconducting wire according to an aspect of the present invention includes: a substrate having a first major surface and a second major surface located opposite the first major surface; and a layer of superconducting material disposed on the first major surface of the substrate. Along at least a part of the superconducting wire in a direction in which the superconducting wire extends, a superconducting material layer is provided so as to cover a side surface of the substrate in a width direction of the substrate and to cover at least a part of the second main surface. The thickness of the layer of superconducting material on the first major surface varies in the width direction. The maximum thickness of the layer of superconducting material on the second major surface is less than the maximum thickness of the layer of superconducting material on the first major surface.

Advantageous effects of the invention

According to the above, in the superconducting wire in which the superconducting material layer is formed on the substrate, local peeling of the superconducting material layer can be suppressed. In this way, a superconducting wire having stable superconducting characteristics can be realized.

Drawings

Fig. 1 is a schematic cross-sectional view showing the configuration of a superconducting wire in a first embodiment.

Fig. 2 is a schematic sectional view showing the configuration of a multilayer stack in the first embodiment.

Fig. 3 is a schematic cross-sectional view showing the configuration of a multilayer stack of superconducting wires in a comparative example.

Fig. 4 is a flowchart showing a superconducting wire manufacturing method in the first embodiment.

Fig. 5 is a schematic cross-sectional view illustrating a superconducting wire manufacturing method in the first embodiment.

Fig. 6 is a schematic cross-sectional view illustrating a superconducting wire manufacturing method in the first embodiment.

Fig. 7 is a schematic cross-sectional view illustrating a superconducting wire manufacturing method in the first embodiment.

Fig. 8 is a schematic cross-sectional view illustrating a superconducting wire manufacturing method in the first embodiment.

Fig. 9 is a schematic cross-sectional view showing the configuration of a superconducting wire according to a first modification in the first embodiment.

Fig. 10 is a schematic cross-sectional view showing the configuration of a superconducting wire according to a second modification in the first embodiment.

Fig. 11 is a schematic sectional view showing the configuration of a superconducting wire in the second embodiment.

Fig. 12 is a schematic sectional view showing the configuration of a superconducting wire in the third embodiment.

Fig. 13 is a schematic sectional view showing the configuration of a superconducting wire in the fourth embodiment.

Fig. 14 is a flowchart showing a superconducting wire manufacturing method in the fourth embodiment.

Fig. 15 is a schematic sectional view showing the configuration of a superconducting wire in a fifth embodiment.

Fig. 16 is a flowchart showing a superconducting wire manufacturing method in the fifth embodiment.

Fig. 17 is a diagram schematically showing the configuration of a cutter used for the wire thinning step.

Fig. 18 is a schematic sectional view showing a superconducting wire manufacturing method in a fifth embodiment.

Fig. 19 is a schematic cross-sectional view showing the configuration of a superconducting wire according to a modification of the fifth embodiment.

Detailed Description

[ description of embodiments of the invention ]

First, the respective aspects of the present invention will be described one by one.

(1) A superconducting wire 10 (refer to fig. 1) according to an aspect of the present invention includes a substrate 1 and a superconducting material layer 5. The substrate 1 includes a first main surface 1a and a second main surface 1b located opposite to the first main surface 1 a. A layer of superconducting material 5 is provided on the first main surface 1a of the substrate 1. Along at least a part of superconducting wire 10 in the direction in which superconducting wire 10 extends, superconducting material layer 5 is provided so as to cover a side surface (at least one of first side surface 1c and second side surface 1 d) of substrate 1 in the width direction of substrate 1 and to cover at least a part of second main surface 1 b. The thickness of the superconducting material layer 5 on the first main surface 1a varies in the width direction. The maximum thickness T2 of the layer of superconducting material 5 located on the second main surface 1b of the substrate 1 is smaller than the maximum thickness T1 of the layer of superconducting material 5 located on the first main surface 1 a.

Thus, superconducting material layer 5 is formed so as to cover first main surface 1a of substrate 1, and also cover the side surface of substrate 1 and at least a portion of second main surface 1 b. Therefore, at the end portions in the width direction of substrate 1, the bonding strength between substrate 1 and superconducting material layer 5 can be improved. Accordingly, local peeling of superconducting material layer 5 can be suppressed, and thus deterioration of the superconducting characteristics of superconducting wire 10 can be suppressed.

Since maximum thickness T2 is smaller than maximum thickness T1, the strength of superconducting material layer 5 on second main surface 1b is smaller than the strength of superconducting material layer 5 on first main surface 1 a. Therefore, the possibility that the superconducting material layer 5 on the second main surface 1b is broken before the superconducting material layer 5 on the first main surface 1a is broken due to the stress applied to the superconducting material layer 5 is increased. Therefore, it may be prioritized to prevent the cracking or deformation of the superconducting material layer 5 on the first main surface 1a, as opposed to preventing the cracking or deformation of the superconducting material layer 5 on the second main surface 1 b. The layer of superconducting material 5 on the first main surface 1a is a major part of the path through which the superconducting current flows. Since protection of this portion is prioritized, deterioration of the superconducting characteristics of superconducting wire 10 can be effectively suppressed. Thereby, superconducting wire 10 having stable superconducting characteristics can be realized.

(2) Superconducting wire 10 also comprises an intermediate layer 3 disposed between first main surface 1a of substrate 1 and superconducting material layer 5. Along at least a part of superconducting wire 10 in the direction in which superconducting wire 10 extends, intermediate layer 3 is provided so as to cover the side surface of substrate 1 and to cover at least a part of second main surface 1 b. The maximum thickness T4 of the intermediate layer 3 located on the second main surface 1b is smaller than the maximum thickness T3 of the intermediate layer 3 located on the first main surface 1a (refer to fig. 8).

Therefore, the bonding strength between the substrate 1 and the intermediate layer 3 can be improved at the end portions in the width direction of the substrate 1, and therefore, the peeling of the intermediate layer 3 from the substrate 1 can be suppressed. Accordingly, peeling of the superconducting material layer 5 due to peeling of the intermediate layer 3 can be suppressed. Since the maximum thickness T4 is smaller than the maximum thickness, the strength of the intermediate layer 3 located on the second main surface 1b is smaller than the strength of the intermediate layer 3 located on the first main surface 1 a. Therefore, the possibility that the intermediate layer 3 located on the second main surface 1b is broken before the intermediate layer 3 located on the first main surface 1a is broken due to the stress applied to the intermediate layer 3 is increased. Therefore, it is possible to give priority to preventing the cracking or deformation or the like of the intermediate layer 3 and the superconducting material layer 5 on the first main surface 1a, over preventing the cracking or deformation or the like of the intermediate layer 3 and the superconducting material layer 5 on the second main surface 1 b.

(3) Superconducting wire 10 further includes protective layer 7 formed on superconducting material layer 5. Along at least a part of superconducting wire 10 in the direction in which superconducting wire 10 extends, protective layer 7 is provided to cover the side surface of substrate 1 and to cover at least a part of second main surface 1 b. The maximum thickness T6 of the protective layer 7 located on the second main surface 1b is smaller than the maximum thickness T5 of the protective layer 7 located on the first main surface 1 a.

Thus, protective layer 7 may be formed to cover superconducting material layer 5, superconducting material layer 5 covering the side surface of substrate 1 and covering at least a portion of second major surface 1 b. It is possible to protect the superconducting material layer 5 and to help prevent peeling of the superconducting material layer 5. Since the maximum thickness T6 is smaller than the maximum thickness T5, the total thickness of the superconducting material layer 5 and the protective layer 7 on the second main surface 1b is smaller than the superconducting material layer 5 and the protective layer 7 on the first main surface 1a and thus is less strong. Therefore, the possibility that the superconducting material layer 5 on the second main surface 1b is broken before the superconducting material layer 5 on the first main surface 1a is broken is not suppressed.

(4) With regard to the superconducting wire 10 (refer to fig. 1), the thickness of the superconducting material layer 5 on the first main surface 1a varies in the width direction in such a manner that the thickness of the middle portion of the superconducting material layer 5 in the width direction is larger than the thickness of at least one end of the superconducting material layer 5 in the width direction. Since such occurrence of local peeling of superconducting material layer 5 of superconducting wire 10 can also be suppressed, deterioration of the superconducting characteristics of superconducting wire 10 can be suppressed. Thereby being capable of exhibiting stable superconducting characteristics.

(5) With regard to the superconducting wire 10 (refer to fig. 11), the thickness of the superconducting material layer 5 on the first main surface 1a varies in the width direction in such a manner that the thickness of at least one end of the superconducting material layer 5 in the width direction is larger than the thickness of the middle portion of the superconducting material layer 5 in the width direction. Since such occurrence of local peeling of superconducting material layer 5 of superconducting wire 10 can also be suppressed, deterioration of the superconducting characteristics of superconducting wire 10 can be suppressed. Thereby being capable of exhibiting stable superconducting characteristics.

(6) With respect to superconducting wire 10, along at least a part of superconducting wire 10 in the direction in which superconducting wire 10 extends, superconducting material layer 5 located at one end of second main surface 1b in the width direction is separated from superconducting material layer located at the other end of second main surface 1b in the width direction. In other words, one end of the superconducting material layer 5 in the width direction is formed to extend from above the first side surface 1c to above a part of the second main surface 1b, and the other end of the superconducting material layer 5 in the width direction is formed to extend from above the second side surface 1d to above a part of the second main surface 1 b. On the second main surface 1b, both ends of the superconducting material layer 5 are separated from each other. Since such occurrence of local peeling of superconducting material layer 5 of superconducting wire 10 can also be suppressed, deterioration of the superconducting characteristics of superconducting wire 10 can be suppressed. Thereby being capable of exhibiting stable superconducting characteristics.

(7) With regard to superconducting wire 10, superconducting material layer 5 is disposed directly or indirectly on first main surface 1a of substrate 1. The fact that the layer of superconducting material 5 is indirectly arranged on the first main surface 1a means that the intermediate layer 3 or another layer/layers is/are located between the first main surface 1a and the layer of superconducting material 5. In the case where superconducting material layer 5 is provided directly on first main surface 1a and the case where superconducting material layer 5 is provided indirectly on first main surface 1a, the bonding strength between substrate 1 and superconducting material layer 5 can be improved, and therefore local peeling of superconducting material layer 5 can be suppressed.

(8) With respect to superconducting wire 10 (refer to fig. 15), first main surface 1a of substrate 1 includes a bent portion. Thus, the surface area of the first main surface 1a is larger than the surface area of the flat first main surface 1a of the substrate 1. The bonding strength between the first main surface 1a and the superconducting material layer 5 can be further improved. Accordingly, the effect of suppressing the occurrence of peeling of the superconducting material layer 5 can be enhanced.

(9) With respect to superconducting wire 10 (refer to fig. 19), the bent portion is located at an end portion of first main surface 1a of substrate 1 in the width direction of substrate 1. Therefore, at the end portion of first main surface 1a in the width direction, the uniformity of the contraction of superconducting material layer 5 and the contraction of substrate 1 during cooling can be improved. Therefore, the superconducting material layer 5 can be suppressed from peeling.

(10) With regard to the superconducting wire 10, the superconducting material layer 5 is made of an oxide superconducting material. Since local peeling of the superconducting material layer can be suppressed, an oxide superconducting wire having stable superconducting characteristics can be realized.

[ detailed description of the invention ]

Embodiments of the present invention will be described below based on the drawings. In the following drawings, the same or corresponding portions are denoted by the same reference numerals, and the description thereof will not be repeated.

< first embodiment >

Structure of superconducting wire

Fig. 1 is a schematic cross-sectional view showing the configuration of a superconducting wire in a first embodiment. Fig. 1 shows a cross section in a direction transverse to the extending direction of a superconducting wire 10 in the first embodiment. Therefore, the direction transverse to the plane of the drawing is the longitudinal direction of the superconducting wire, and the superconducting current in the superconducting material layer 5 flows in the direction transverse to the plane of the drawing. In the schematic cross-sectional views in fig. 1 and subsequent drawings, the difference between the vertical dimension (hereinafter also referred to as the "thickness direction") and the horizontal dimension (hereinafter also referred to as the "width direction") is small for easy recognition of the drawings. However, in practice, the dimension in the thickness direction of the cross section is much smaller than the dimension in the width direction of the cross section.

Referring to fig. 1, a superconducting wire 10 in the first embodiment has a long shape (tape shape) of a rectangular cross section, and a relatively large surface of the wire extending in the longitudinal direction of the long shape is defined herein as a main surface. Superconducting wire 10 includes substrate 1, intermediate layer 3, superconducting material layer 5, protective layer 7, and stabilization layer 9.

The substrate 1 has a first main surface 1a and a second main surface 1 b. The second main surface 1b is located opposite to the first main surface 1 a. The substrate 1 also has a first side surface 1c and a second side surface 1d opposite to the first side surface 1 c. Preferably, the substrate 1 is made of, for example, metal and has a long shape (strip shape) of a rectangular cross section. In order to wind the superconducting wire in a coil shape, it is preferable that the substrate 1 extends for a long distance of about 2 km.

More preferably, an orientation-aligned metal substrate is used as the substrate 1. An orientation-aligned metal substrate refers to a substrate in which the crystal orientations are aligned in two axial directions within the plane of the substrate surface. For the orientation-aligned metal substrate, it is preferable to use, for example, an alloy of at least two metals selected from nickel (Ni), copper (Cu), chromium (Cr), manganese (Mn), cobalt (Co), iron (Fe), palladium (Pd), silver (Ag), and gold (Au). These metals and another metal or alloy may be stacked together. For example, an alloy such as SUS, which is a high-strength material, may also be used. The material of the substrate 1 is not limited to the above-described material, and for example, a material other than metal may be used.

For example, the superconducting wire 10 has a dimension of about 4mm to 10mm in the width direction. In order to increase the density of the current flowing in superconducting wire 10, a smaller cross-sectional area of substrate 1 is preferable. However, since the strength of the substrate 1 may be reduced by making the thickness of the substrate 1 too thin (in the vertical direction in fig. 1), the thickness of the substrate 1 is preferably about 0.1 mm.

The intermediate layer 3 is formed on the first main surface 1a of the substrate 1. A superconducting material layer 5 is formed on a main surface (upper main surface in fig. 1) of the intermediate layer 3 opposite to its main surface facing the substrate 1. That is, superconducting material layer 5 is disposed on first major surface 1a of substrate 1, and intermediate layer 3 is located between superconducting material layer 5 and substrate 1. The material forming the intermediate layer 3 is preferably yttria-stabilized zirconia (YSZ), ceria (CeO)₂) Magnesium oxide (MgO), yttrium oxide (Y)₂O₃) Or strontium titanate (SrTiO)₃). These materials have extremely low reactivity to the superconducting material layer 5, and do not impair the superconducting characteristics of the superconducting material layer 5 even at the boundary adjacent to the superconducting material layer 5. Particularly in the case of using a metal as a material for forming substrate 1, the intermediate layer may function to alleviate a difference in alignment between superconducting material layer 5 and substrate 1 having crystal alignment in the surface thereof, thereby preventing metal atoms from escaping from substrate 1 into superconducting material layer 5 during formation of superconducting material layer 5 at high temperature. The material forming the intermediate layer 3 is not particularly limited to the above-described materials.

The intermediate layer 3 may be composed of multiple layers. In the case where the intermediate layer 3 is composed of a plurality of layers, the layers constituting the intermediate layer 3 may be formed of various materials different from each other, or some of the layers constituting the intermediate layer 3 may be made of the same material.

The superconducting material layer 5 is a thin film layer in the superconducting wire 10, and a superconducting current flows in this superconducting material layer 5. Although the superconducting material is not particularly limited, the superconducting material is preferably, for example, an RE-123-based oxide superconductor. RE-123 based oxide superconductors are referred to as REBa₂Cu₃O_y(y is 6 to 8, more preferably 6.8 to 7, and RE represents yttrium or a rare earth element such as Gd, Sm, Ho, etc.). In order to improve the magnitude of the superconducting current flowing in the superconducting material layer 5, the superconducting material layer 5 preferably has a thickness of 0.5 μm to 10 μm.

The protective layer 7 is formed on a main surface (upper main surface in fig. 1) of the superconducting material layer 5 opposite to the main surface thereof facing the intermediate layer 3. Preferably, the protective layer 7 is made of, for example, silver (Ag) or a silver alloy, and has a thickness of not less than 0.1 μm and not more than 50 μm.

The above-mentioned substrate 1, intermediate layer 3, superconducting material layer 5 and protective layer 7 constitute a multilayer stack 20. The stabilizing layer 9 is arranged to cover the periphery of the multilayer stack 20. In the present embodiment, the stabilizing layer 9 is arranged to cover the outer periphery of the multilayer stack 20, i.e. substantially the entire outermost surface of the multilayer stack 20. It should be noted that the "periphery of the multilayer stack" of the present invention is not limited to the entire periphery, and may be only the surface of the bulk multilayer stack.

The stabilization layer 9 is formed of a highly conductive metal foil, plating, or the like. The stabilizing layer 9 together with the protective layer 7 serves as a bypass for the commutation of the current in the superconducting material layer 5 when the superconducting material layer 5 is transformed from the superconducting state into the normally conducting state. The material forming the stabilization layer 9 is preferably copper (Cu), a copper alloy, or the like, for example. Although the thickness of the stabilization layer 9 is not particularly limited, the thickness is preferably 10 μm to 500 μm in order to physically protect the protective layer 7 and the superconducting material layer 5.

Fig. 2 is a schematic sectional view showing the configuration of the multilayer stack 20 in the first embodiment. Fig. 2 shows a cross section in a direction transverse to the extending direction of the superconducting wire 10 in the first embodiment.

In the multilayer stack 20 of the first embodiment, the superconducting material layer 5 is provided so as to cover the side surface of the substrate 1 in the width direction (left-right direction in fig. 2) and to cover at least a part of the second main surface 1 b.

Specifically, in the multilayer stack 20 shown in fig. 2, one end of the superconducting material layer 5 in the width direction is formed to extend from above the first side surface 1c to above a part of the second main surface 1b, and the other end of the superconducting material layer 5 in the width direction is formed to extend from above the second side surface 1d to above a part of the second main surface 1 b. On the second main surface 1b, both ends of the superconducting material layer 5 are separated from each other. In other words, the layer of superconducting material 5 is arranged to completely cover the first main surface 1a and the side surfaces 1c, 1d of the substrate 1 and to partially cover the second main surface 1 b.

This configuration makes it possible to improve the bonding strength between the substrate 1 and the superconducting material layer 5, as compared with a conventional superconducting wire in which the superconducting material layer 5 covers only the first main surface 1a of the substrate 1.

Details are as follows. When a superconducting wire, which forms a superconducting material layer as a ceramic layer on a metal substrate, is cooled to its critical temperature, stress is generated between the metal substrate and the superconducting material layer due to a difference in thermal expansion coefficient between the metal and the ceramic material. Specifically, when the superconducting wire is cooled, each layer in the wire contracts. At this time, since the superconducting material layer has a smaller thermal expansion coefficient than the metal substrate, the superconducting material layer cannot contract to the same extent as the metal substrate and is thus subjected to stress. Therefore, in the conventional superconducting wire, the superconducting material layer may be peeled off particularly at the end portion in the width direction of the substrate.

In the superconducting wire in which the intermediate layer is also located between the substrate and the superconducting material layer, the intermediate layer as the ceramic layer may be peeled off from the end portion in the width direction of the substrate, such as the superconducting material layer described above. The delamination of the superconducting material layer or the intermediate layer makes, for example, the superconducting material layer more likely to be cracked or deformed, which may cause deterioration of superconducting characteristics.

In superconducting wire 10 of the first embodiment, superconducting material layer 5 extends from

side surfaces

1c, 1d of substrate 1 over at least a portion of second main surface 1 b. Therefore, the bonding area between the substrate 1 and the superconducting material layer 5 can be increased as compared with the conventional superconducting wire, and thus the bonding strength between the substrate 1 and the superconducting material layer 5 can be enhanced. Therefore, when superconducting wire 10 is cooled, the uniformity of the contraction of superconducting material layer 5 with the contraction of substrate 1 is improved. It is therefore possible to suppress the peeling of the superconducting material layer 5 from the substrate 1. As a result, the superconducting material layer 5 can be prevented from cracking or deforming, and thus deterioration of the superconducting characteristics of the superconducting wire 10 can be suppressed.

In the multilayer stack 20 shown in fig. 2, the intermediate layer 3 is arranged to completely cover the first main surface 1a and the side surfaces 1c, 1d of the substrate 1 and to partially cover the second main surface 1 b. Therefore, similarly to the bonding strength between the substrate 1 and the superconducting material layer 5, the bonding strength between the substrate 1 and the intermediate layer 3 can be improved. The peeling of the intermediate layer 3 from the substrate 1 can be suppressed. Accordingly, peeling of the superconducting material layer 5 due to peeling of the intermediate layer 3 can be suppressed. As shown in fig. 2, preferably, the superconducting material layer 5 covers the end portion of the intermediate layer 3 in the width direction. Therefore, the effect of suppressing the peeling of the intermediate layer 3 can be enhanced.

In the multilayer stack 20 shown in fig. 2, the protective layer 7 is arranged to completely cover the first main surface 1a and the side surfaces 1c, 1d of the substrate 1 and to partially cover the second main surface 1 b. Thus, protective layer 7 may be formed to cover superconducting material layer 5, and superconducting material layer 5 covers side surfaces 1c, 1d and second main surface 1b of substrate 1. The protective layer 7 thus protects the superconducting material layer 5 and may help prevent peeling of the superconducting material layer 5. Preferably, as shown in fig. 2, the protective layer 7 covers the end portion of the superconducting material layer 5 in the width direction. Therefore, the effect of suppressing the peeling of the superconducting material layer 5 can be enhanced.

As long as superconducting material layer 5, intermediate layer 3, and protective layer 7 in superconducting wire 10 in the first embodiment cover at least a portion of second main surface 1b along at least a portion of superconducting wire 10 in the direction in which superconducting wire 10 extends (longitudinal direction), the bonding strength between substrate 1 and superconducting material layer 5 and intermediate layer 3 can be improved.

In the multilayer stack 20 shown in fig. 2, the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 on the first main surface 1a each have a sectional shape protruding in the middle in the width direction thereof. Specifically, the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 each have a convex-shaped upper surface that is curved upward. Therefore, the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 on the first main surface 1a each have a thickness that varies in the width direction. In the example of fig. 2, the apex of this curve is located approximately at the center of the upper surface in the width direction. Therefore, each of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 has a thickness at the middle portion in the width direction larger than that at the end portions in the width direction.

In the multilayer stack 20, the maximum thickness T2 of the layer of superconducting material 5 located on the second main surface 1b is smaller than the maximum thickness T1 of the layer of superconducting material 5 located on the first main surface 1a (T2< T1).

Since T2 is smaller than T1, the strength of the superconducting material layer 5 on the second main surface 1b is smaller than the strength of the superconducting material layer 5 on the first main surface 1 a. Therefore, when superconducting material layer 5 is subjected to stress applied from substrate 1, the possibility that superconducting material layer 5 located on second main surface 1b is broken before superconducting material layer 5 located on first main surface 1a is broken increases. Thus, it is more preferable to protect the superconducting material layer 5 located on the first main surface 1a from the stress applied to the superconducting material layer 5. Since the superconducting material layer 5 located on the first main surface 1a is a main part of a path through which a superconducting current flows, it is possible to preferentially protect this part to effectively suppress deterioration of superconducting characteristics.

If T2 is much smaller than T1, there is a possibility that sufficient bonding strength cannot be maintained between second main surface 1b and superconducting material layer 5. Therefore, it is preferable that the ratio of T2 to T1 (T2/T1) is 0.1% or more and 95% or less. When this ratio is 95% or less, the strength of the superconducting material layer 5 on the second main surface 1b is ensured to be smaller than the strength of the superconducting material layer 5 on the first main surface 1a, and therefore, the above-described effects can be sufficiently produced. In contrast, when this ratio is less than 0.1%, sufficient bonding strength between substrate 1 and superconducting material layer 5 on second main surface 1b cannot be maintained, and the above-described effect may not be sufficiently produced.

Further, the superconducting wire 10 in the first embodiment can produce advantageous effects as compared with the comparative example shown in fig. 3. Fig. 3 is a schematic cross-sectional view showing the configuration of a multilayer stack of superconducting wires in a comparative example. Fig. 3 shows a cross section of the superconducting wire in the comparative example in a direction transverse to the extending direction of the superconducting wire.

Referring to fig. 3, the multilayer stack 200 of the comparative example is substantially similar to the multilayer stack 20 shown in fig. 2. The multilayer stack 200 differs from the multilayer stack 20 shown in fig. 2, however, in that the former comprises an intermediate layer 3, a layer of superconducting material 5 and a protective layer 7, which are arranged to cover the first main surface 1a of the substrate 1 and to partially cover the side surfaces 1c, 1d of the substrate 1.

In other words, with respect to the multilayer stack 200, the superconducting material layer 5 and the intermediate layer 3 do not extend above the second main surface 1 b. Thus, the multilayer stack 20 shown in fig. 2 is larger in both the bonding area between the substrate 1 and the superconducting material layer 5 and the bonding area between the substrate 1 and the intermediate layer 3, compared to the multilayer stack 200.

When cooled, the substrate 1 contracts not only in the width direction but also in the thickness direction. In the multilayer stack 20 shown in fig. 2, the superconducting material layer 5 and the intermediate layer 3 extend above the second main surface 1b, and therefore, the uniformity of shrinkage not only in the width direction but also in the thickness direction will be high. In contrast, with regard to the multilayer stack 200, although the uniformity of shrinkage in the width direction of the substrate 1 can be provided by the superconducting material layer 5 and the intermediate layer 3 located on the side surfaces 1c, 1d, the uniformity 1 of shrinkage in the thickness direction of the substrate may be low.

Further, in the cross section of the multilayer stack 20 shown in fig. 2, the width-direction end portions of the superconducting material layers 5 are respectively U-shaped. Therefore, the width-direction end of the superconducting material layer 5 is substantially in a state of catching the second main surface 1 b. In this state, in terms of structure, the end portion functions as a hook for fixing the superconducting material layer 5 to the substrate 1. This makes it possible to realize a structure having higher resistance to stress from the substrate 1 than in the comparative example.

For the above reasons, superconducting wire 10 in the first embodiment can produce a higher effect of suppressing the peeling of superconducting material layer 5 and/or intermediate layer 3 from substrate 1 than the superconducting wires in the comparative examples.

In the first embodiment, the intermediate layer 3 and the superconducting material layer 5 covering the side surface of the substrate 1 and covering at least a part of the second main surface 1b may be formed to cover the first side surface 1c and the second side surface 1d, respectively, as shown in fig. 1 and 2, or formed to cover only one of the first side surface 1c and the second side surface 1 d. In other words, the intermediate layer 3 and the superconducting material layer 5 may be provided so as to cover at least one of the first side surface 1c and the second side surface 1d and at least a part of the second main surface 1 b. Both of these configurations can increase the bonding strength between the substrate 1, the intermediate layer 3 and the superconducting material layer 5, as compared with the conventional superconducting wire and the comparative example (fig. 3).

Method for manufacturing superconducting wire

Next, referring to fig. 4 to 8, a method of manufacturing the superconducting wire in the first embodiment is described.

Fig. 4 is a flowchart showing a superconducting wire manufacturing method in the first embodiment. The present embodiment is described below, as an example, in connection with a method of manufacturing superconducting wire 10 using substrate 1 having a width of 4mm that has been subjected to wire thinning.

Referring to fig. 4, a substrate preparation step (S10) is first performed. Specifically, referring to fig. 5, a band-shaped substrate 1 having a desired width (for example, width: 4mm) formed of an orientation-aligned metal substrate is prepared. The substrate 1 has a first main surface 1a and a second main surface 1b located opposite to the first main surface 1a, and a first side surface 1c and a second side surface 1d located opposite to the first side surface 1 c. The thickness of the substrate 1 may be appropriately adjusted to meet any purpose, and may be generally in the range of 10 μm to 500 μm. The thickness of the substrate 1 is, for example, approximately 100 μm.

Next, an intermediate layer forming step of forming the intermediate layer 3 on the substrate 1 is performed (S20 in fig. 4). Specifically, referring to fig. 6, the intermediate layer 3 is formed on the first main surface 1a of the substrate 1. As a method of forming the intermediate layer 3, any method may be used. For example, a physical vapor deposition method such as a Pulsed Laser Deposition (PLD) method may be used.

Next, a superconducting material layer forming step of forming the superconducting material layer 5 on the intermediate layer 3 is performed (S30 in fig. 4). Specifically, referring to fig. 7, a superconducting material layer 5 made of an RE-123-based oxide superconductor is formed on the main surface (upper main surface in fig. 7) of the intermediate layer 3 opposite to the main surface thereof facing the substrate 1. As a method of forming the superconducting material layer 5, any method may be used. For example, the layer may be formed using a gas phase method, a liquid phase method, or a combination thereof. Examples of the vapor phase method are a laser vapor deposition method, a sputtering method, an electron beam vapor deposition method, and the like. This step may be performed by at least one of a laser vapor deposition method, a sputtering method, an electron beam method, and an organometallic deposition method to form the superconducting material layer 5 excellent in crystal orientation alignment of the surface and surface smoothness thereof.

Next, a protective layer forming step of forming the protective layer 7 on the superconducting material layer 5 is performed (S40 in fig. 4). Specifically, referring to fig. 8, a protective layer 7 made of silver (Ag) or a silver alloy is formed by a physical vapor deposition method such as sputtering, an electroplating method, or the like on the main surface (upper main surface in fig. 8) of the superconducting material layer 5 opposite to the main surface thereof facing the intermediate layer 3. The protective layer 7 may be formed to protect the surface of the superconducting material layer 5. Thereafter, oxygen annealing, i.e., heating in an oxygen atmosphere (oxygen introducing step) is performed to introduce oxygen into the superconducting material layer 5. Through the above steps, a multilayer stack 20 having a width-directional dimension of about 30mm was formed.

Next, a stabilization layer forming step of forming the stabilization layer 9 on the periphery of the multilayer stack 20 is performed (S50 in fig. 4). Specifically, the stabilization layer 9 made of copper (Cu) or a copper alloy is formed by known plating so as to cover the periphery of the multilayer stack 20, i.e., to cover substantially the entire outermost surface of the multilayer stack 20. The method of forming the stabilization layer 9 may be a combination of copper foils other than electroplating. Through the above steps, the superconducting wire 10 in the first embodiment shown in fig. 1 is manufactured.

In the multilayer stack 20 shown in fig. 8, the maximum thickness T4 of the intermediate layer 3 located on the second main surface 1b is preferably smaller than the maximum thickness T3 of the intermediate layer 3 located on the first main surface 1a (T4< T3).

When T4 is less than T3, the strength of the intermediate layer 3 located on the second main surface 1b is less than the strength of the intermediate layer 3 located on the first main surface 1 a. Therefore, when the intermediate layer 3 is subjected to stress applied from the substrate 1, the possibility that the intermediate layer 3 located on the second main surface 1b is broken before the intermediate layer 3 located on the first main surface 1a is broken increases. Therefore, the intermediate layer 3 located on the first main surface 1a is preferentially protected from the stress applied to the intermediate layer 3. Thus, for example, the superconducting material layer 5 on the first main surface 1a can be preferentially protected from breakage or deformation.

In the multilayer stack 20, the maximum thickness T6 of the protective layer 7 on the second main surface 1b is preferably smaller than the maximum thickness T5 of the protective layer 7 on the first main surface 1a (T6< T5).

When T6 is smaller than T5, the total thickness of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 on the second main surface 1b is smaller, and therefore the strength is smaller than that of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 on the first main surface 1 a. Therefore, the possibility of cracking the superconducting material layer 5 on the second main surface 1b before cracking the superconducting material layer 5 on the first main surface 1a is not suppressed.

Modification of the first embodiment

Referring to fig. 9 and 10, a modification of the superconducting wire in the first embodiment is described.

Fig. 9 is a schematic cross-sectional view showing the configuration of a superconducting wire 10A according to a first modification in the first embodiment. Fig. 9 shows a cross section in a direction transverse to the extending direction of superconducting wire 10A.

Referring to fig. 9, basically, superconducting wire 10A has a structure similar to that of superconducting wire 10 shown in fig. 1, except that the shape of stabilization layer 9 of superconducting wire 10A is different from that of superconducting wire 10.

In superconducting wire 10A, the thickness of stabilizer layer 9 located at the width-direction end portion of first main surface 1a of substrate 1 is larger than the thickness of stabilizer layer 9 located above the width-direction middle portion of first main surface 1 a. The thickness of the stabilizer layer 9 located at the widthwise end portion of the second main surface 1b of the substrate 1 is also larger than the thickness of the stabilizer layer 9 located above the widthwise middle portion of the second main surface 1 b.

In superconducting wire 10A, intermediate layer 3 and superconducting material layer 5 are also formed to extend from upper side surfaces 1c, 1d of substrate 1 over a portion of second main surface 1 b. The maximum thickness T2 of the layer of superconducting material 5 situated on the second main surface 1b is smaller than the maximum thickness T1 of the layer of superconducting material 5 situated on the first main surface 1 a. Furthermore, the maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the second main surface 1b is smaller than the maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the first main surface 1 a. Thus, superconducting wire 10A can produce effects similar to those of superconducting wire 10 shown in fig. 1.

The method of manufacturing the superconducting wire 10A basically has similar features to the method of manufacturing the superconducting wire in the first embodiment described above based on fig. 4 to 8, except that the conditions for forming the stabilizer layer in the stabilizer layer forming step (S50 in fig. 4) of the preceding method are different from those of the first embodiment. For example, when the stabilization layer 9 is formed using an electroplating method to cover the periphery of the multilayer stack 20 with the stabilization layer 9, current may concentrate at the corners of the multilayer stack 20. As a result, the plating layer covering the corners is relatively thick. The stabilization layer 9 shown in fig. 9 can thus be formed. Superconducting wire 10A is obtained in this manner.

Fig. 10 is a schematic cross-sectional view showing the configuration of a superconducting wire 10B according to a second modification in the first embodiment. Fig. 10 shows a cross section in a direction transverse to the extending direction of superconducting wire 10B.

Referring to fig. 10, a superconducting wire 10B of a substantially second modification has a structure similar to that of superconducting wire 10 shown in fig. 1, except that the structure of multilayer stack 20 is different from that of multilayer stack 20 shown in fig. 2.

In superconducting wire 10B, protective layer 7 on second main surface 1B is provided so as to completely cover second main surface 1B. In superconducting wire 10B, intermediate layer 3 and superconducting material layer 5 are also formed to extend from above upper side surfaces 1c, 1d of substrate 1 to above a portion of second main surface 1B. The maximum thickness T2 of the layer of superconducting material 5 situated on the second main surface 1b is smaller than the maximum thickness T1 of the layer of superconducting material 5 situated on the first main surface 1 a. Furthermore, the maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the second main surface 1b is smaller than the maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the first main surface 1 a. Thus, superconducting wire 10B can produce effects similar to those of superconducting wire 10 shown in fig. 1.

The method of manufacturing the superconducting wire 10B basically has the similar features to the method of manufacturing the superconducting wire in the first embodiment described above based on fig. 4 to 8. Except that the conditions for forming the protective layer in the protective layer forming step (fig. 4, S40 in fig. 8) of the preceding method are different from those of the first embodiment. For example, when the protective layer 7 is formed on the main surface of the superconducting material layer 5 opposite to the main surface thereof facing the intermediate layer 3 using an electroplating method, the second main surface 1b may be completely plated to form the protective layer 7 as shown in fig. 10. In this way, superconducting wire 10B is obtained.

Also in the modification shown in fig. 9 and 10, as long as the superconducting material layer 5 covers a part of the second main surface 1b along at least a part of the superconducting wire in the longitudinal direction, it is possible to improve the bonding strength between the substrate 1 and the superconducting material layer 5. The intermediate layer 3 may cover a portion of the second main surface 1b, and the protective layer 7 may cover at least a portion of the second main surface 1b along at least a portion of the superconducting wire in the longitudinal direction.

< second embodiment >

Fig. 11 is a schematic sectional view showing the configuration of a superconducting wire 10C in the second embodiment. Fig. 11 shows a cross section in a direction transverse to the extending direction of superconducting wire 10C.

Referring to fig. 11, a superconducting wire 10C in substantially the second embodiment has a structure similar to that of the superconducting wire 10 shown in fig. 1, except that the structure of the multilayer stack 20 is different from that of the multilayer stack 20 shown in fig. 2.

In superconducting wire 10C, intermediate layer 3, superconducting material layer 5, and protective layer 7 on first major surface 1a each protrude at opposite ends in the width direction, and thus have a cross section with its middle portion in the width direction retracted. In other words, the upper surface of each of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 has a concave shape curved toward the substrate 1. Therefore, the thicknesses of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 on the first main surface 1a each vary in the width direction. In the example of fig. 11, the thickness of each of the width-direction end portions of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 is larger than the thickness of the width-direction middle portion.

In superconducting wire 10C, maximum thickness T2 of superconducting material layer 5 on second main surface 1b is also smaller than maximum thickness T1 of superconducting material layer 5 on first main surface 1 a. The maximum thickness of the intermediate layer 3 and the protective layer 7 on the second main surface 1b is smaller than the maximum thickness of the intermediate layer 3 and the protective layer 7 on the first main surface 1a, respectively. Thus, superconducting wire 10C can produce effects similar to those of superconducting wire 10 shown in fig. 1.

The method of basically manufacturing the superconducting wire 10C has similar features to the method of manufacturing the superconducting wire in the first embodiment described above based on fig. 4 to 8, except that the conditions for forming these layers in the intermediate layer forming step (S20 in fig. 4, fig. 6), the superconducting material layer forming step (S30 in fig. 4, fig. 7), and the protective layer forming step (S40 in fig. 4, fig. 8) are different from those in the first embodiment.

< third embodiment >

Fig. 12 is a schematic sectional view showing the configuration of a superconducting wire 10D in the third embodiment. Fig. 12 shows a cross section in a direction transverse to the extending direction of superconducting wire 10D.

Referring to fig. 12, a superconducting wire 10D of the third embodiment basically has a structure similar to that of superconducting wire 10 shown in fig. 2, except that the structure of multilayer stack 20 is different from that of multilayer stack 20 shown in fig. 2.

In superconducting wire 10D, intermediate layer 3, superconducting material layer 5, and protective layer 7 on second main surface 1b are provided so as to completely cover second main surface 1b, respectively. In superconducting wire 10D, maximum thickness T2 of superconducting material layer 5 on second major surface 1b is also smaller than maximum thickness T1 of superconducting material layer 5 on first major surface 1 a. The maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the second main surface 1b is also smaller than the maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the first main surface 1 a. Thus, superconducting wire 10D can produce effects similar to those of superconducting wire 10 shown in fig. 1.

As long as superconducting material layer 5 completely covers second main surface 1b along at least a portion of superconducting wire 10D in the longitudinal direction, it will be possible to improve the bonding strength between substrate 1 and superconducting material layer 5. The intermediate layer 3 may completely cover the second main surface 1b, and the protective layer 7 may completely cover the second main surface 1b along at least a part of the superconducting wire 10D in the longitudinal direction.

The method of basically manufacturing the superconducting wire 10D has similar features to the method of manufacturing the superconducting wire in the first embodiment described above based on fig. 4 to 8, except that the conditions for forming these layers in the intermediate layer forming step (S20 in fig. 4, fig. 6), the superconducting material layer forming step (S30 in fig. 4, fig. 7), and the protective layer forming step (S40 in fig. 4, fig. 8) are different from those in the first embodiment.

< fourth embodiment >

Fig. 13 is a schematic sectional view showing the configuration of a multilayer stack in a superconducting wire 10E in the fourth embodiment. Fig. 13 shows a cross section in a direction transverse to the extending direction of superconducting wire 10E.

Referring to fig. 13, a superconducting wire 10E of the fourth embodiment basically has a structure similar to that of superconducting wire 10 shown in fig. 1, except that the structure of multilayer stack 20 is different from that of multilayer stack 20 shown in fig. 2.

In superconducting wire 10E, intermediate layer 3, superconducting material layer 5, and protective layer 7 are provided so as to completely cover first main surface 1a and first side surface 1c of substrate 1, and to partially cover second main surface 1 b. In contrast, the second side surface 1d of the substrate 1 is not covered with the intermediate layer 3, the superconducting material layer 5, and the protective layer 7.

In superconducting wire 10E, intermediate layer 3, superconducting material layer 5, and protective layer 7 on first main surface 1a protrude at one end in the width direction, respectively. In other words, the upper surfaces of each of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 have a convex shape that is curved outward. Therefore, the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 on the first main surface 1a each have a thickness that varies in the width direction. In the example shown in fig. 13, the thickness of each of the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 is larger at one end in the width direction than at the other end in the width direction.

In superconducting wire 10E, maximum thickness T2 of superconducting material layer 5 on second major surface 1b is also smaller than maximum thickness T1 of superconducting material layer 5 on first major surface 1 a. The maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the second main surface 1b is also smaller than the maximum thickness of each of the intermediate layer 3 and the protective layer 7 on the first main surface 1 a. Thus, superconducting wire 10E can produce effects similar to those of superconducting wire 10 shown in fig. 1.

Fig. 14 is a flowchart showing a superconducting wire manufacturing method in the fourth embodiment. Referring to fig. 14, basically the superconducting wire manufacturing method in the fourth embodiment has similar features to the superconducting wire manufacturing method in the first embodiment described above based on fig. 4 to 8. However, the former method differs from the first embodiment in that the former method includes a line thinning step.

Referring to fig. 14, a substrate preparation step (S10) is first performed. Specifically, a substrate 1 having a wide band shape, which is formed of an orientation-aligned metal substrate, is prepared. The width of the substrate 1 at this time may be, for example, a width (for example, 8mm) approximately twice the width (for example, 4mm) of the substrate 1 in the superconducting wire 10E.

Next, an intermediate layer forming step (S20), a superconducting material layer forming step (S30), and a protective layer forming step (S40) are sequentially performed on the wide substrate 1. The intermediate layer forming step, the superconducting material layer forming step, and the protective layer forming step are performed similarly to the respective steps in the first embodiment. These steps are thus performed to form a wide multi-layer stack 20.

Next, a wire thinning step of cutting the wide multilayer stack 20 into multilayer stacks having a predetermined width (e.g., 4mm) is performed (S60). Specifically, mechanical slitting was performed using a rotary blade, and the multilayer stack of 8mm width was mechanically slit into a multilayer stack of 4mm width.

In the line thinning step (S60), for example, the multilayer stack 20 having a dimension in the width direction of about 8mm is cut in half in the width direction, and two multilayer stacks 20 having a width of 4mm are produced. The multilayer stack 20 shown in fig. 13 is one of these multilayer stacks. The respective cut surfaces of the two multilayer stacks 20 exposed by this cutting may be formed as one end surface in the width direction, respectively. In the multilayer stack 20 shown in fig. 13, the second side surface 1d of the substrate 1 is exposed and not covered by the intermediate layer 3, the superconducting material layer 5 and the protective layer 7. Another multi-layer stack 20 (not shown) facing the cut surface of the multi-layer stack 20 shown in fig. 13 exposes the first side 1c of the substrate 1. In particular, in the multilayer stack 20, not illustrated, the intermediate layer 3, the layer of superconducting material 5 and the protective layer 7 completely cover the first main surface 1a, the side surfaces 1d and partially cover the second main surface 1b of the substrate 1. In contrast, the first side surface 1c is not covered with the intermediate layer 3, the superconducting material layer 5, and the protective layer 7 and is thus exposed.

In the line thinning step (S60), laser processing may be performed to cut the multilayer stack into fine lines. The multilayer stack 20 shown in fig. 13 can also be obtained by adjusting the conditions of the laser treatment.

Next, a stabilization layer forming step of forming a stabilization layer 9 on the periphery of the multilayer stack 20 that has undergone line thinning is performed (S50). The stable layer forming step is performed similarly to the first embodiment. The above-described steps are performed to thereby manufacture superconducting wire 10E shown in fig. 13.

< fifth embodiment >

Fig. 15 is a schematic sectional view showing the configuration of a multilayer stack of superconducting wires 10F in the fifth embodiment. Fig. 15 shows a cross section in a direction transverse to the extending direction of superconducting wire 10F.

Referring to fig. 15, a superconducting wire 10F in a substantially fifth embodiment has a structure similar to that of superconducting wire 10 shown in fig. 1, except that the structure of multilayer stack 20 is different from that of multilayer stack 20 shown in fig. 2.

In superconducting wire 10F, first main surface 1a of substrate 1 has a convex shape curved outward. The apex of the curve is located approximately at the center of the first main surface 1a in the width direction. The end of the curve is located at the end of the first main surface 1a in the width direction. The intermediate layer 3, the superconducting material layer 5, and the protective layer 7 are formed along the first main surface 1 a. Therefore, the upper surface of the multilayer stack 20 (the upper surface of the protective layer 7) also has a convex shape that is curved outward. The intermediate layer 3, the superconducting material layer 5, and the protective layer 7 each have a thickness that varies in the width direction. In the multilayer stack 20 shown in fig. 15, the maximum thickness T2 of the layer of superconducting material 5 situated on the second main surface 1b is also smaller than the maximum thickness T1 of the layer of superconducting material 5 situated on the first main surface 1 a.

With respect to superconducting wire 10F, first main surface 1a is curved. Therefore, the surface area of first main surface 1a may be increased as compared to substrate 1 having flat first main surface 1 a. The intermediate layer 3 and the superconducting material layer 5 are formed to completely cover the first main surface 1a having the bent portion, and therefore the bonding area between the substrate 1 and the intermediate layer 3 and the bonding area between the substrate 1 and the superconducting material layer 5 are increased. Accordingly, the bonding strength between the substrate 1 and the intermediate layer 3 and the bonding strength between the substrate 1 and the superconducting material layer 5 can be further improved.

The curved surface portion may be the entire first main surface 1a as shown in fig. 15, or a part of the first main surface 1 a. The curved surface portion may have a convex shape curved outward, or may be curved toward the second main surface 1b (concave shape).

Fig. 16 is a flowchart showing a superconducting wire manufacturing method in the fifth embodiment. Referring to fig. 16, basically, the superconducting wire manufacturing method in the fifth embodiment has similar features to the superconducting wire manufacturing method in the first embodiment described above based on fig. 4 to 8. However, the former method differs from the first embodiment in that the former method includes a line thinning step.

Referring to fig. 16, a substrate preparation step (S10) is first performed. Specifically, a substrate 1 having a wide band shape (width of about 30mm) formed of an orientation-aligned metal substrate was prepared.

Next, a wire thinning step of cutting the substrate 1 having a width of 30mm into substrates 1 each having a predetermined width (for example, 4mm) is performed (S70). Specifically, as shown in fig. 17, the substrate 1 having a width of 30mm was mechanically slit into substrates 1 having a width of 4mm by using a rotary blade for mechanical slitting.

Fig. 17 schematically shows the configuration of the slitter used for the wire thinning step. The structure of the substrate 1 diced by the dicer 30 is shown on the right side of fig. 17.

Referring to fig. 17, the cutter 30 includes a plurality of rotary blades 31 and a plurality of spacers 32. For example, the cutter 30 includes seven rotary blades 31 in total. Three rotary blades 31 having a width of about 4mm are arranged on the upper rotary shaft of the cutter 30. Between the rotary blades 31 adjacent to each other in the rotation axis direction, spacers 32 are disposed. Four rotary blades 31 having a width of about 4mm are also disposed on the lower rotary shaft of the cutter 30. The width of the rotary blade 31 disposed on the upper and lower rotary shafts may be set to any width.

As shown in fig. 17, the substrate 1 diced with the rotary blade 31 in contact with the second main surface 1b has a sectional shape in which the first main surface 1a protrudes in the middle in the width direction (the first main surface 1a has a convex shape) due to adjustment of dicing conditions such as a gap between adjacent rotary blades 31 and vertical overlap of the rotary blades 31. In this way, the substrate 1 having the cross-sectional shape as shown in fig. 18 can be obtained. In contrast, the substrate 1 diced with the rotary blade 31 in contact with the first main surface 1a has a sectional shape in which the second main surface 1b protrudes at the middle in the width direction (the second main surface 1b has a convex shape) due to adjustment of dicing conditions such as a gap between adjacent rotary blades 31 and vertical overlap of the rotary blades 31.

As described above, the mechanical dicing cuts the substrate 1 by shearing of the upper rotary blade 31 and the opposite lower rotary blade 31. The resulting thin lines (substrates 1) respectively have curved edges depending on the application direction (cutting direction) of the rotary blade 31. Specifically, with respect to a thin line (substrate 1e) cut from the first main surface 1a side surface by the upper rotary blade 31, the edge of the substrate 1 is bent in a direction toward the first main surface 1 a. In contrast, with respect to the thin line (substrate 1f) cut by the lower rotary blade 31 from the side surface of the second main surface 1b, the edge of the substrate 1 is curved in the direction toward the second main surface 1b, and therefore the first main surface 1a has a convex shape.

With regard to the mechanical slitting shown in fig. 17, the width of the rotary blade 31 applied to the first main surface 1a is the same as the width of the rotary blade 31 applied to the second main surface 1 b. However, the rotary blade 31 applied to the second main surface 1b may have a predetermined width (e.g., 4mm), and the rotary blade 31 applied to the first main surface 1a may have a narrower width. This can increase the number of thin lines (substrate 1 has convex first main surface 1a shown in fig. 18) obtained by side-cutting from second main surface 1 b.

Next, an intermediate layer forming step (S20), a superconducting material layer forming step (S30), and a protective layer forming step (S40) are sequentially performed on the substrate 1 shown in fig. 18. The intermediate layer forming step, the superconducting material layer forming step, and the protective layer forming step are performed similarly to the first embodiment. These steps are performed to thereby form the multilayer stack 20 shown in fig. 15.

Next, a stabilization layer forming step of forming the stabilization layer 9 on the periphery of the multilayer stack 20 is performed (S50). The stable layer forming step is performed similarly to the first embodiment. These steps are performed to thereby manufacture superconducting wire 10F shown in fig. 15.

Modification of the fifth embodiment

Fig. 19 is a schematic sectional view showing the configuration of a superconducting wire 10G according to a modification of the fifth embodiment. Fig. 19 shows a cross section in a direction transverse to the extending direction of superconducting wire 10G.

Referring to fig. 19, a superconducting wire 10G substantially according to the modification has a structure similar to that of superconducting wire 10 shown in fig. 1, except that the structure of multilayer stack 20 is different from that of multilayer stack 20 shown in fig. 2.

With respect to superconducting wire 10G, first main surface 1a of substrate 1 has a bent portion at an end portion of substrate 1 in the width direction. Therefore, the first main surface 1a has a convex shape curved outward. The intermediate layer 3, the superconducting material layer 5, and the protective layer 7 each have a thickness that varies in the width direction. With regard to superconducting wire 10G, maximum thickness T2 of superconducting material layer 5 on second major surface 1b is also smaller than maximum thickness T1 of superconducting material layer 5 on first major surface 1 a. The maximum thickness of the intermediate layer 3 and the protective layer 7 on the second main surface 1b is smaller than the maximum thickness of the intermediate layer 3 and the protective layer 7 on the first main surface 1a, respectively.

Since the bent portion is located at the end portion of the substrate 1 in the width direction, the conformity of the contraction of the intermediate layer 3 and the superconducting material layer 5 to the contraction of the substrate 1 can be improved at the end portion of the first main surface 1a in the width direction. Therefore, the intermediate layer 3 and the superconducting material layer 5 can be prevented from peeling off from the substrate 1.

Next, a method for manufacturing superconducting wire 10G shown in fig. 19 will be described. The basic superconducting wire 10G may be obtained by performing the steps (S10 to S70) shown in fig. 16. In the above-described line thinning step (S70), the wide substrate 1 may be cut into portions each having a predetermined width by laser processing, and the first main surface 1a of the substrate 1 obtained by cutting may be subjected to a process for forming a bent portion at an end portion of the first main surface 1a in the width direction of the substrate 1.

With regard to the configuration in which the superconducting material layer is provided so as to cover the side surface of the substrate and cover at least a part of the second main surface in the first to fifth embodiments, the configuration in which each of the intermediate layer, the superconducting material layer, and the protective layer covers the side surface of the substrate and at least a part of the second main surface has been described above. However, the present invention is not limited to this configuration, but also includes a configuration in which the intermediate layer and the superconducting material layer cover the side surface of the substrate and cover at least a part of the second main surface; a configuration in which only the superconducting material layer covers the side surface of the substrate and covers at least a portion of the second main surface; and a configuration in which the superconducting material layer and the protective layer cover the side surface of the substrate and cover at least a portion of the second main surface. Among these configurations, a configuration in which the intermediate layer and the superconducting material layer cover the side surface of the substrate and cover at least a part of the second main surface is preferable, because alignment of the orientation of the superconducting material layer can be improved not only on the first main surface but also on the side surface of the substrate and the second main surface of the substrate, and peeling of the intermediate layer can be prevented.

Although the configuration in which the stabilization layer is formed so as to cover the periphery of the multilayer stack is shown above in connection with the first to fifth embodiments, the stabilization layer may be provided on at least the upper surface of the multilayer stack. In this case, after forming the stabilizer layer on the protective layer, in order to protect the superconducting wire, an insulating coating may be formed to cover the periphery of the superconducting wire.

It is to be understood that the embodiments disclosed herein are presented by way of illustration, not of limitation, in all respects. It is intended that the scope of the invention be defined by the claims, rather than the description above, and that all modifications and variations that are equivalent in meaning and scope to the claims be included therein.

List of reference numerals

1. 1e, 1f substrate; 3 an intermediate layer; 5 a layer of superconducting material; 7, a protective layer; 9 a stabilizing layer; 10. 10A-10G superconducting wire; 20, stacking a plurality of layers; 30, a cutter; 31 a rotary blade; 32 spacers.

Claims

1. A superconducting wire comprising:

a substrate having a first major surface and a second major surface located opposite the first major surface; and

a layer of superconducting material disposed on the first major surface of the substrate,

the superconducting material layer is provided so as to cover a side surface of the substrate in a width direction of the substrate and to cover at least a part of the second main surface along at least a part of the superconducting wire in a direction in which the superconducting wire extends,

the thickness of the superconducting material layer on the first major surface varies in the width direction,

the maximum thickness of the layer of superconducting material on the second major surface is less than the maximum thickness of the layer of superconducting material on the first major surface.

2. The superconducting wire of claim 1 further comprising an intermediate layer disposed between the first major surface of the substrate and the layer of superconducting material, wherein

The intermediate layer is provided so as to cover the side surface of the substrate and at least a part of the second main surface along at least a part of the superconducting wire in a direction in which the superconducting wire extends, and

the maximum thickness of the interlayer on the second major surface is less than the maximum thickness of the interlayer on the first major surface.

3. The superconducting wire as claimed in claim 1 or 2, further comprising a protective layer formed on the superconducting material layer, wherein

The protective layer is provided so as to cover the side surface of the substrate and to cover at least a part of the second main surface along at least a part of the superconducting wire in a direction in which the superconducting wire extends, and

the maximum thickness of the protective layer on the second major surface is less than the maximum thickness of the protective layer on the first major surface.

4. The superconducting wire of claim 1 wherein

The thickness of the superconducting material layer on the first main surface varies in the width direction in such a manner that a thickness of a central portion of the superconducting material layer in the width direction is larger than a thickness of at least one end of the superconducting material layer in the width direction.

5. The superconducting wire of claim 1 wherein

The thickness of the superconducting material layer on the first main surface varies in the width direction in such a manner that the thickness of at least one end of the superconducting material layer in the width direction is larger than the thickness of the middle portion of the superconducting material layer in the width direction.

6. The superconducting wire of claim 1 wherein

The superconducting material layer located at one end of the second main surface in the width direction is separated from the superconducting material layer located at the other end of the second main surface in the width direction along at least a part of the superconducting wire in a direction in which the superconducting wire extends.

7. The superconducting wire of claim 1,

the layer of superconducting material is disposed directly or indirectly on the first major surface of the substrate.

8. The superconducting wire of claim 1 wherein

The first major surface of the substrate includes a bend.

9. The superconducting wire of claim 8,

the bent portion is located at one end of the first main surface in the width direction.

10. The superconducting wire of claim 1 wherein

The superconducting material layer is made of an oxide superconducting material.